Biology subjects

Gama-Carvalho, M.

Publications and source records attributed to Gama-Carvalho, M..

7 recordsLinked to original sources

bioRxiv2025

miR-34c-5p is a novel regulator of T cell differentiation that targets FOXP3

MicroRNAs regulate key genes and pathways essential for T cell differentiation and function; however, many remain poorly characterized. We previously identified miR-34c-5p as a T cell receptor-inducible microRNA in naive CD4 T cells, but its role in immune regulation remained largely unexplored. In this study, we mapped miR-34c expression across multiple sort-purified CD4 T cell subsets and found that its induction is restricted to FOXP3 cells, both natural regulatory T cells (Tregs) and cells undergoing inducible Treg (iTreg) differentiation trajectory. miR-34c expression correlates with high FOXP3 levels and is absent in conventional memory effector subsets. Functional studies using miR-34c antagomiRs reveal that miR-34c limits iTreg differentiation by restraining FOXP3 expression. Mechanistically, we show that FOXP3 activates miR-34c transcription through direct binding to its promoter, while miR-34c targets the FOXP3 3'UTR, establishing a negative feedback loop. Together, our findings identify miR-34c as a FOXP3-responsive miRNA that fine-tunes iTreg development via post-transcriptional repression of FOXP3, uncovering a novel layer of regulatory control in T cell responses.

immunology↗

bioRxiv2024

Small non-coding RNA content in plasma-derived extracellular vesicles distinguish ataxic SCA3 mutation carriers from pre-ataxic and control subjects

Spinocerebellar ataxia type 3 (SCA3), a neurodegenerative disorder caused by a CAG expansion in the ATXN3 gene, is the most common spinocerebellar ataxia subtype worldwide. Currently, there is no therapy to stop or prevent disease progression. Promising therapeutic strategies are emerging, but their translation into clinical practice requires sensitive and reliable biomarkers. Blood circulating extracellular vesicles constitute a promising source of biomarkers with potential to track alterations of the central nervous system due to their ability to cross the blood brain barrier. Here, we perform sequencing analysis of small RNAs from plasma-derived extracellular vesicles from SCA3 mutation carriers (10 pre-ataxic and 10 ataxic) and 12 control subjects to identify potential RNA biomarker candidates for this disease. Data showed that plasma-derived extracellular vesicles from ataxic SCA3 mutation carriers are enriched in mitochondrial, nuclear, and nucleolar RNA biotypes compared to pre-ataxic and control subjects. Moreover, ataxic mutation carriers could be discriminated from control and pre-ataxic subjects based on the miRNAs or piRNAs content, but not tRNA. Furthermore, we identified a subset of differentially expressed miRNAs and piRNAs that clearly differentiate ataxic mutation carriers from pre-ataxic and control subjects. These findings open new avenues for further investigation on the role of these RNAs in the pathogenesis of SCA3 and their potential as biomarkers for this disease.

neuroscience↗

bioRxiv2022

Human Satellite 1 (HSAT1) analysis provides novel evidence of pericentromeric transcription

Pericentromeric regions of human chromosomes are composed of tandem-repeated and highly organized sequences named satellite DNAs. Although being known for a long time as the most AT-rich fraction of the human genome, classical satellite HSAT1 has been disregarded in genomic and transcriptional studies, falling behind other human satellites in terms of knowledge. The path followed herein trails with HSAT1 isolation and cloning, followed by in silico analysis. Monomer copy number and expression data was obtained in a wide variety of human cell lines, with greatly varying profiles in tumoral/non-tumoral samples. HSAT1 was mapped in human chromosomes and applied in in situ transcriptional assays. Additionally, it was possible to observe the nuclear organization of HSAT1 transcripts and further characterize them by 3 RACE-Seq. Size-varying polyadenylated HSAT1 transcripts were detected, which possibly accounts for the intricate regulation of alternative polyadenylation. As far as we know, this work pioneers HSAT1 transcription studies. With the emergence of new human genome assemblies, acrocentric pericentromeres are becoming relevant characters in disease and other biological contexts. HSAT1 sequences and associated noncoding RNAs will most certainly prove significant in the future of HSAT research.

genomics↗

bioRxiv2022

Specialized Tfh cell subsets driving type-1 and type-2 humoral responses in lymphoid tissue

Effective antibody responses are essential to generate protective humoral immunity. Different inflammatory signals polarize T cells towards an appropriate effector phenotype during an infection or immunization. Th1 and Th2 cells have been associated with the polarization of humoral responses for several decades. However, it is now established that T follicular helper cells (Tfh) have a unique ability to access the B cell follicle and support the Germinal Centre (GCs) responses by providing help to B cells. We investigated the specialization of Tfh cells induced under type-1 and type-2 conditions. We first studied homogenous Tfh cell populations generated by adoptively transferred TCR-transgenic T cells in mice immunized with type-1 and type-2 adjuvants. Using a machine learning approach, we established a gene expression signature that discriminates Tfh cells polarized towards type-1 and type-2 response, defined as Tfh1 and Tfh2 cells. The Tfh1 and Tfh2 distinct signature was validated against datasets of Tfh cells induced following LCMV or helminth infection. Using single-cell transcriptomics, we also dissected the heterogeneity of Tfh cells from the two immunizing conditions. Our results show that Tfh cells acquire a specialized function under distinct types of immune responses, but with the coexistence of a small population of Tfh cells of the alternative type. Furthermore, the specific molecular hallmarks of Tfh1 and Tfh2 cells identified herein offer putative new targets for tuning humoral responses.

immunology↗

bioRxiv2022

Analysis of pre-symptomatic Drosophila models for ALS and SMA reveals convergent impact on functional protein complexes linked to neuro-muscular degeneration

Spinal Muscular Atrophy (SMA) and Amyotrophic Lateral Sclerosis (ALS) share phenotypic and molecular commonalities, including the fact that they can be caused by mutations in ubiquitous proteins involved in RNA metabolism, namely SMN, TDP-43 and FUS. Although this suggests the existence of common disease mechanisms, there is currently no model to explain the resulting motor neuron dysfunction. In this work we generated a parallel set of Drosophila models for adult-onset RNAi and tagged neuronal expression of the fly orthologues of the three human proteins, named Smn, TBPH and Caz, respectively. We profiled nuclear and cytoplasmic bound mRNAs using a RIP-seq approach and characterized the transcriptome of the RNAi models by RNA-seq. To unravel the mechanisms underlying the common functional impact of these proteins on neuronal cells, we devised a computational approach based on the construction of a tissue-specific library of protein functional modules, selected by an overall impact score measuring the estimated extent of perturbation caused by each gene knockdown. Transcriptome analysis revealed that the three proteins do not bind to the same RNA molecules and that only a limited set of functionally unrelated transcripts is commonly affected by their knock-down. However, our integrative approach revealed they exert a concerted effect on protein functional modules, acting through distinct targets. Most strikingly, functional annotation revealed that these modules are involved in critical cellular pathways for motor neurons, including neuromuscular junction function. Furthermore, selected modules were found to be significantly enriched in orthologues of human neuronal disease genes. The results presented here show that SMA and ALS disease-associated genes linked to RNA metabolism functionally converge on neuronal protein complexes, providing a new hypothesis to explain the common motor neuron phenotype. The functional modules identified represent promising biomarkers and therapeutic targets, namely given their alteration in asymptomatic settings.

neuroscience↗

bioRxiv2022

Thymus formation in uncharted embryonic territories.

The thymus is a conserved organ among vertebrates, derived from the endoderm of distinct pharyngeal pouches (PP), whose location and number vary across species. Together with reports of sporadic ectopic thymus locations in mice and humans, this suggests that the potential to make a thymus resides in a broader region of the PP endoderm than previously ascribed. Using the chick-quail chimera system, we explore this hypothesis and test the capacity of non-canonical pouches to participate in thymus formation. We further ask if the local mesenchyme of pharyngeal arches (PA) could also play a role in the regulation of thymus formation. After testing several embryonic tissue associations, we mapped the pharyngeal endoderm regions with thymus potential to the second and third/fourth pharyngeal pouches (2PP and 3/4PP). We further identified mesenchyme regions that regulate this potential to the 3/4 pharyngeal arches and to the dorsal region of the second arch, with positive and negative influences, respectively. Transcriptomic analysis of these tissues helped us revealing a common genetic program in the PP endoderm linked to thymus potential in addition to finding distinct signalling pathways involved in the cellular interactions with the mesenchyme of the pharyngeal arches that result in modulating this potential. Together, these results provide new information about the initial specification of thymus primordia in the embryo that may contribute to improving the development of thymus organoid systems. GO_SCPLOWRAPHICALC_SCPLOWO_SCPCAP C_SCPCAPO_SCPLOWABSTRACTC_SCPLOW O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=110 SRC="FIGDIR/small/483697v2_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@a12a67org.highwire.dtl.DTLVardef@e6d49eorg.highwire.dtl.DTLVardef@90d7b0org.highwire.dtl.DTLVardef@140672e_HPS_FORMAT_FIGEXP M_FIG C_FIG

developmental biology↗

bioRxiv2019

A role for DIS3L2 over human nonsense-mediated mRNA decay targets

The nonsense-mediated decay (NMD) pathway selectively degrades mRNAs carrying a premature translation-termination codon but also regulates the abundance of a large number of physiological mRNAs that encode full-length proteins. In human cells, NMD-targeted mRNAs are degraded by endonucleolytic cleavage and exonucleolytic degradation from both 5 and 3 ends. This is done by a process not yet completely understood that recruits decapping and 5-to-3 exonuclease activities, as well as deadenylating and 3-to-5 exonuclease exosome activities. In yeast, DIS3/Rrp44 protein is the catalytic subunit of the exosome, but in humans, there are three known paralogues of this enzyme: DIS3, DIS3L1, and DIS3L2. DIS3L1 and DIS3L2 exoribonucleases localize in the same compartment where NMD occurs, but little is known about their role in this process. In order to unveil the role of DIS3L2 in NMD, here we show that some NMD-targets accumulate in DIS3L2-depleted cells. mRNA half-life analysis further supports that these NMD-targets are in fact DIS3L2 substrates. Besides, we observed that DIS3L2 acts over full-length transcripts, through a process that also involves UPF1. Moreover, DIS3L2-mediated decay is dependent on the activity of the terminal uridylyl transferases Zcchc6/11 (TUT7/4). Together, our findings establish a role for DIS3L2 and uridylation in NMD.

molecular biology↗